Streptococcal pyrogenic exotoxins (SPE) A, B, and C will be purified by methods involving repeated alcohol precipitation with solubilization in acetate buffer at pH 4.0 followed by column chromatography on Sephadex G-73 and QUAE-Sephadex. Additional investigations on methods to increase the yield of toxin and improve methods of purification will be continued. The purified toxins will be used to raise specific antisera in rabbits; these antisera will be used in passive hemagglutination and hemagglutination inhibition assays for toxin-typing and anti-toxin determinations. The methods will be used to survey group A streptococci isolated from rheumatic fever patients to determine the distribution of A, B, and C toxins and for the detection of new distinct types. New approaches to the preparation of immunogenic toxoids will involve insolubilization with homologous methylated serum albumins. A basic immunologic study on the role of hypersensitivity in the toxicity of SPE will include: Mitogenic activity on B and T lymphocytes from sensitized and non-sensitized animals, the release of lymphokines, induction of cytotoxic activity by sensitized lymphocytes or target cells and the development of skin sensitivity and its passive transfer to non-primed animals. The target site and mechanism of immunosuppression by SPE will be investigated using cell transfer experiments and in vitro antigenic stimulation. It should be possible to determine whether SPE interference of the immunologic response involves macrophages, lymphocytes or both.